Yes, an invoice can be saved as a draft even if all the mandatory fields are not filled.
Any draft bill can be converted to active only after all the mandatory fields are filled.
Yes. Similar to draft invoices, you can save a draft payment.
Find the draft payment on an invoice and ensure all the mandatory fields are filled.
You should then be able to convert it to active.
Yes, you can delete a draft invoice. If the invoice had a draft payment linked, it will also be deleted.
Similar to draft bills, draft invoice payments can also be deleted.
No, it does not. Financial reports are only affected once the invoices are active.
No, it does not. Financial reports are only affected once the payments are active.
Yes, the currency setting on an invoice does not affect the ability to save it as a draft.
Yes, you can save an invoice payment as a draft even if it is in non-base currency.